Circulating systems are known in which the cooled down water content of the hot water distribution line is conveyed back into the hot water tank via a recirculation pipe as disclosed in our earlier U.S. Pat. No. 5,143,049. Subsequent retrofit of a recirculation system requires additional piping which may be difficult to install. A different type of hot water recovery system is disclosed in U.S. Pat. No. 5,009,572 Imhoff et al. and U.S. Pat. No. 5,277,219 Lund, in which a recirculation pump is switched on if the hot water temperature near the faucet drops below a pre-determined level or as soon as a hot water faucet is opened. To economize the hot water usage the pump conveys the cooled-down content of the hot water distribution line back through the cold water distribution line into the water heater. Thus the faucets in the distribution line receive warm water when the cooled-down water content between the water heater and the faucets has been pumped into the cold water distribution line.
The aforesaid U.S. Pat. Nos. 5,009,572 Imhoff et al.; 5,143,049 Laing et al.; and 5,277,219 Lund are incorporated into this specification by this reference.
The prior art systems that recirculate the cooled-down portion of the hot water distribution line directly through the cold water distribution line have several drawbacks. The most serious is the fact that the cold water distribution line is first filled with lukewarm, if not hot water. If cold water is needed right after a recirculation cycle, the user must wait several seconds for that heated water to be purged from the cold water distribution line. Another drawback results from the use of various valves in association with the recirculation pump which can cause pressure waves to resound through the plumbing network.
The present invention avoids these drawbacks.